External graph parameters are serialized in XML format with following schema:

<?xml version="1.0" encoding="UTF-8"?>
<schema xmlns="http://www.w3.org/2001/XMLSchema" targetNamespace="http://www.example.org/GraphParameters"
    xmlns:tns="http://www.example.org/GraphParameters" elementFormDefault="qualified">

    <element name="GraphParameters" type="tns:GraphParametersType"></element>

    <complexType name="GraphParametersType">
        <sequence>
            <element name="GraphParameter" type="tns:GraphParameterType"
                maxOccurs="unbounded" minOccurs="0"></element>
        </sequence>
    </complexType>

    <complexType name="GraphParameterType">
        <sequence>
            <element name="attr" type="tns:attrType" maxOccurs="unbounded"
                minOccurs="0">
            </element>
            <choice>
                <element name="SingleType" type="tns:SingleTypeType"></element>
                <element name="ComponentReference" type="tns:ComponentReferenceType">
                </element>
            </choice>
        </sequence>
        <attribute name="name" type="string" use="required"></attribute>
        <attribute name="value" type="string" use="required"></attribute>
        <attribute name="dynamicValue" type="string"></attribute>
        <attribute name="secure" type="boolean"></attribute>
        <attribute name="description" type="string"></attribute>
        <attribute name="public" type="boolean"></attribute>
        <attribute name="required" type="boolean"></attribute>
        <attribute name="label" type="string"></attribute>
        <attribute name="defaultHint" type="string"></attribute>
        <attribute name="category" type="string"></attribute>
    </complexType>

    <complexType name="ComponentReferenceType">
        <attribute name="referencedComponent" type="string"></attribute>
        <attribute name="referencedProperty" type="string"></attribute>
    </complexType>

    <complexType name="SingleTypeType">
        <attribute name="name" type="string"></attribute>
    </complexType>

    <complexType name="attrType">
        <attribute name="name" type="string"></attribute>
    </complexType>
</schema>

For example:

<?xml version="1.0" encoding="UTF-8"?>
<GraphParameters>
    <GraphParameter name="PROJECT" value=".">
        <attr name="description">Project root path</attr>
    </GraphParameter>
    <GraphParameter name="CONN_DIR" value="${PROJECT}/conn">
        <attr name="description">Default folder for external connections</attr>
    </GraphParameter>
    <GraphParameter name="DATAIN_DIR" value="${PROJECT}/data-in">
        <attr name="description">Default folder for input data files</attr>
    </GraphParameter>
    <GraphParameter name="DATAOUT_DIR" value="${PROJECT}/data-out">
        <attr name="description">Default folder for output data files</attr>
    </GraphParameter>
    <GraphParameter name="DATATMP_DIR" value="${PROJECT}/data-tmp">
        <attr name="description">Default folder for temporary data files</attr>
    </GraphParameter>
    <GraphParameter name="GRAPH_DIR" value="${PROJECT}/graph">
        <attr name="description">Default folder for transformation graphs (grf)</attr>
    </GraphParameter>
    <GraphParameter label="Public parameter" name="PUBLIC_PARAM" public="true" required="true" value="default value">
        <SingleType name="multiline"/>
    </GraphParameter>
</GraphParameters>